A digital image may contain one or more regions of interest (ROIs). In many applications, only image data contained within the one or more ROIs of a digital image may need to be retained for further processing and for information extraction by computers. Efficient and accurate identification of these ROIs thus constitutes a critical first step in these applications, particularly for applications that handle high-volume and/or real-time digital images. Each ROI of a digital image may contain pixels forming patches with drastic variation in texture and pattern, making accurate and efficient identification of the boundary between these ROIs and the rest of the digital image a challenging task for a computer.